The manual coffee machine requires that the filter holder is manually refilled every time a coffee is made, whereas the refilling in an automatic machine is automatic.
A coffee machine of semiautomatic type allows both operations.
In particular, the operation system of these machines provides for the hot water contacting the powdered coffee to cover a specific path in order to make the infusion. The obtained coffee beverage is sensible to different parameters used in the process, such as for example the used coffee quality, its grain size, the water temperature and pressure during the infusion cycle.
Nowadays coffee machines present on the market include a filter holder, that the operator manually connects to the infusion unit of the machine.
The filter holder can be filled manually with powdered coffee and subsequently connected to the infusion unit or filled automatically with powdered coffee only after its correct positioning on the infusion unit.
In this latter case, powdered coffee is then compressed and then the infusion unit releases a predetermined water amount at temperature and pressure that are optimal for preparing coffee with the best organoleptic characteristics.
In both cases, once the coffee has been prepared the filter holder is manually detached from the machine and the exhausted powdered coffee is thrown away.
In this way the filter holder can be reused for preparing another coffee.
This kind of machine can be equipped with one or more infusion unit and, consequently, with several filter holders.
Usually for each infusion unit there are several filter holders, at least one for espresso coffees and one for double espresso coffees.
In these machines if the filter holder is at room temperature, for example when the first coffee is made after a time interval that has allowed the cooling thereof, its mass tends to cool the hot water during the infusion process thereby causing a decline of qualitative features of the coffee made.
In machines up to now manufactured, the filter holder is maintained hot by keeping it attached to the infusion unit of the coffee machine. If several filter holders are available in the machine equipment per each infusion unit, it is evident that only one will be maintained at working temperature, whereas the others will be at room temperature.